How to backup all collections from mongodb (raspberry)

After some problems with my raspberry power supply and mongo 3.0 I decided to make a dayly backup.
Sometimes happened that, after an unexpected shutdown (for an high load average and not too much power), some mongo collections may be broken. If it’ll happen without any backup, the only words you can say are: I’m fuck.

Yeah, I know.. if you install mongo on a 32bit system with only 1GB ram (Raspberry Pi 3), you are probabily (like me) mad.
But! It’s useful for some testing or a micro-system.

So.. the solution

One of the idea that I’ve got is make a dayly backup. I use 3.0 mongo version, but it will be ok for > 3.0 version.
NOTE: you need to install mongotools.